"Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException" 在使用 ImageIcon 添加图像时出现

Question

首先，我在整个背景上应用了面板，然后创建了一个标签以在此处设置图像。 JFrame picture

我看到有很多与空指针异常相关的问题和答案，但没有一个适合我。 ImageIcon 无法获取图像。我什至尝试创建一个文件夹并给出路径，但错误仍然存在。网豆：12.5 jdk:8 请提前帮忙me.Thanks

package com.mycompany.supershop;
import java.awt.Image;
import java.awt.Toolkit;
import javax.print.DocFlavor.URL;
import javax.swing.ImageIcon;
public class add_image extends javax.swing.JFrame {

    public add_image() {
        initComponents();
        
        ImageIcon img= new ImageIcon(Toolkit.getDefaultToolkit().getImage(getClass().getResource("shop_removebg.png"))); 
        Image img1=img.getImage();
        Image img2 = img1.getScaledInstance(jLabel1.getWidth(),jLabel1.getHeight(),Image.SCALE_SMOOTH);
        ImageIcon i=new ImageIcon(img2);
        jLabel1.setIcon(i);


    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jPanel1 = new javax.swing.JPanel();
        jLabel1 = new javax.swing.JLabel();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jLabel1.setText("jLabel1");

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addGap(87, 87, 87)
                .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 112, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(303, Short.MAX_VALUE))
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addGap(33, 33, 33)
                .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 100, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(158, Short.MAX_VALUE))
        );

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addContainerGap())
        );

        pack();
    }                      

    public static void main(String args[]) {
        
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(add_image.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(add_image.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(add_image.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(add_image.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
      
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new add_image().setVisible(true);
            }
        });
    }            
    private javax.swing.JLabel jLabel1;
    private javax.swing.JPanel jPanel1;                
}

错误显示，

> Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at sun.awt.SunToolkit.imageCached(SunToolkit.java:899)
    at sun.lwawt.macosx.LWCToolkit.getImage(LWCToolkit.java:549)
    at com.mycompany.supershop.add_image.<init>(add_image.java:24)
    at com.mycompany.supershop.add_image.run(add_image.java:107)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
    at java.awt.EventQueue.access0(EventQueue.java:97)
    at java.awt.EventQueue.run(EventQueue.java:709)
    at java.awt.EventQueue.run(EventQueue.java:703)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
------------------------------------------------------------------------

问题出在这一行，

ImageIcon img= new ImageIcon(Toolkit.getDefaultToolkit().getImage(getClass().getResource("shop_removebg.png")));

显示错误的请求图像：

picture1 picture2 picture3 picture4

Answer 1

给定项目结构，图像的有效路径字符串为：

"/com/mycompany/supershop/shop_removebg.png"

始终使用 / 前缀表示从类路径的根开始搜索。

"Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException" 在使用 ImageIcon 添加图像时出现

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